misc: pti: Remove driver for deprecated platform

Intel Moorestown and Medfield are quite old Intel Atom based
32-bit platforms, which were in limited use in some Android phones,
tablets and consumer electronics more than eight years ago.

There are no bugs or problems ever reported outside from Intel
for breaking any of that platforms for years. It seems no real
users exists who run more or less fresh kernel on it. The commit
05f4434bc130 ("ASoC: Intel: remove mfld_machine") also in align
with this theory.

Due to above and to reduce a burden of supporting outdated drivers
we remove the support of outdated platforms completely.

Cc: Alexander Shishkin <[e-mail]>
Acked-by: Linus Walleij <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Acked-by: Alexander Shishkin <[e-mail]>
Signed-off-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/driver-api/pti_intel_mid.rst

···
-.. SPDX-License-Identifier: GPL-2.0
-
-=============
-Intel MID PTI
-=============
-
-The Intel MID PTI project is HW implemented in Intel Atom
-system-on-a-chip designs based on the Parallel Trace
-Interface for MIPI P1149.7 cJTAG standard.  The kernel solution
-for this platform involves the following files::
-
-	./include/linux/pti.h
-	./drivers/.../n_tracesink.h
-	./drivers/.../n_tracerouter.c
-	./drivers/.../n_tracesink.c
-	./drivers/.../pti.c
-
-pti.c is the driver that enables various debugging features
-popular on platforms from certain mobile manufacturers.
-n_tracerouter.c and n_tracesink.c allow extra system information to
-be collected and routed to the pti driver, such as trace
-debugging data from a modem.  Although n_tracerouter
-and n_tracesink are a part of the complete PTI solution,
-these two line disciplines can work separately from
-pti.c and route any data stream from one /dev/tty node
-to another /dev/tty node via kernel-space.  This provides
-a stable, reliable connection that will not break unless
-the user-space application shuts down (plus avoids
-kernel->user->kernel context switch overheads of routing
-data).
-
-An example debugging usage for this driver system:
-
-  * Hook /dev/ttyPTI0 to syslogd.  Opening this port will also start
-    a console device to further capture debugging messages to PTI.
-  * Hook /dev/ttyPTI1 to modem debugging data to write to PTI HW.
-    This is where n_tracerouter and n_tracesink are used.
-  * Hook /dev/pti to a user-level debugging application for writing
-    to PTI HW.
-  * `Use mipi_` Kernel Driver API in other device drivers for
-    debugging to PTI by first requesting a PTI write address via
-    mipi_request_masterchannel(1).
-
-Below is example pseudo-code on how a 'privileged' application
-can hook up n_tracerouter and n_tracesink to any tty on
-a system.  'Privileged' means the application has enough
-privileges to successfully manipulate the ldisc drivers
-but is not just blindly executing as 'root'. Keep in mind
-the use of ioctl(,TIOCSETD,) is not specific to the n_tracerouter
-and n_tracesink line discpline drivers but is a generic
-operation for a program to use a line discpline driver
-on a tty port other than the default n_tty:
-
-.. code-block:: c
-
-  /////////// To hook up n_tracerouter and n_tracesink /////////
-
-  // Note that n_tracerouter depends on n_tracesink.
-  #include <errno.h>
-  #define ONE_TTY "/dev/ttyOne"
-  #define TWO_TTY "/dev/ttyTwo"
-
-  // needed global to hand onto ldisc connection
-  static int g_fd_source = -1;
-  static int g_fd_sink  = -1;
-
-  // these two vars used to grab LDISC values from loaded ldisc drivers
-  // in OS.  Look at /proc/tty/ldiscs to get the right numbers from
-  // the ldiscs loaded in the system.
-  int source_ldisc_num, sink_ldisc_num = -1;
-  int retval;
-
-  g_fd_source = open(ONE_TTY, O_RDWR); // must be R/W
-  g_fd_sink   = open(TWO_TTY, O_RDWR); // must be R/W
-
-  if (g_fd_source <= 0) || (g_fd_sink <= 0) {
-     // doubt you'll want to use these exact error lines of code
-     printf("Error on open(). errno: %d\n",errno);
-     return errno;
-  }
-
-  retval = ioctl(g_fd_sink, TIOCSETD, &sink_ldisc_num);
-  if (retval < 0) {
-     printf("Error on ioctl().  errno: %d\n", errno);
-     return errno;
-  }
-
-  retval = ioctl(g_fd_source, TIOCSETD, &source_ldisc_num);
-  if (retval < 0) {
-     printf("Error on ioctl().  errno: %d\n", errno);
-     return errno;
-  }
-
-  /////////// To disconnect n_tracerouter and n_tracesink ////////
-
-  // First make sure data through the ldiscs has stopped.
-
-  // Second, disconnect ldiscs.  This provides a
-  // little cleaner shutdown on tty stack.
-  sink_ldisc_num = 0;
-  source_ldisc_num = 0;
-  ioctl(g_fd_uart, TIOCSETD, &sink_ldisc_num);
-  ioctl(g_fd_gadget, TIOCSETD, &source_ldisc_num);
-
-  // Three, program closes connection, and cleanup:
-  close(g_fd_uart);
-  close(g_fd_gadget);
-  g_fd_uart = g_fd_gadget = NULL;

drivers/misc/Kconfig

···
 	  If you choose to build module, its name will be phantom. If unsure,
 	  say N here.
 
-config INTEL_MID_PTI
-	tristate "Parallel Trace Interface for MIPI P1149.7 cJTAG standard"
-	depends on PCI && TTY && (X86_INTEL_MID || COMPILE_TEST)
-	help
-	  The PTI (Parallel Trace Interface) driver directs
-	  trace data routed from various parts in the system out
-	  through an Intel Penwell PTI port and out of the mobile
-	  device for analysis with a debugging tool (Lauterbach or Fido).
-
-	  You should select this driver if the target kernel is meant for
-	  an Intel Atom (non-netbook) mobile device containing a MIPI
-	  P1149.7 standard implementation.
-
 config TIFM_CORE
 	tristate "TI Flash Media interface support"
 	depends on PCI

drivers/misc/Makefile

···
 obj-$(CONFIG_AD525X_DPOT)	+= ad525x_dpot.o
 obj-$(CONFIG_AD525X_DPOT_I2C)	+= ad525x_dpot-i2c.o
 obj-$(CONFIG_AD525X_DPOT_SPI)	+= ad525x_dpot-spi.o
-obj-$(CONFIG_INTEL_MID_PTI)	+= pti.o
 obj-$(CONFIG_ATMEL_SSC)		+= atmel-ssc.o
 obj-$(CONFIG_DUMMY_IRQ)		+= dummy-irq.o
 obj-$(CONFIG_ICS932S401)	+= ics932s401.o

drivers/misc/pti.c

···
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- *  pti.c - PTI driver for cJTAG data extration
- *
- *  Copyright (C) Intel 2010
- *
- * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- *
- * The PTI (Parallel Trace Interface) driver directs trace data routed from
- * various parts in the system out through the Intel Penwell PTI port and
- * out of the mobile device for analysis with a debugging tool
- * (Lauterbach, Fido). This is part of a solution for the MIPI P1149.7,
- * compact JTAG, standard.
- */
-
-#include <linux/init.h>
-#include <linux/sched.h>
-#include <linux/interrupt.h>
-#include <linux/console.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/tty.h>
-#include <linux/tty_driver.h>
-#include <linux/pci.h>
-#include <linux/mutex.h>
-#include <linux/miscdevice.h>
-#include <linux/intel-pti.h>
-#include <linux/slab.h>
-#include <linux/uaccess.h>
-
-#define DRIVERNAME		"pti"
-#define PCINAME			"pciPTI"
-#define TTYNAME			"ttyPTI"
-#define CHARNAME		"pti"
-#define PTITTY_MINOR_START	0
-#define PTITTY_MINOR_NUM	2
-#define MAX_APP_IDS		16   /* 128 channel ids / u8 bit size */
-#define MAX_OS_IDS		16   /* 128 channel ids / u8 bit size */
-#define MAX_MODEM_IDS		16   /* 128 channel ids / u8 bit size */
-#define MODEM_BASE_ID		71   /* modem master ID address    */
-#define CONTROL_ID		72   /* control master ID address  */
-#define CONSOLE_ID		73   /* console master ID address  */
-#define OS_BASE_ID		74   /* base OS master ID address  */
-#define APP_BASE_ID		80   /* base App master ID address */
-#define CONTROL_FRAME_LEN	32   /* PTI control frame maximum size */
-#define USER_COPY_SIZE		8192 /* 8Kb buffer for user space copy */
-#define APERTURE_14		0x3800000 /* offset to first OS write addr */
-#define APERTURE_LEN		0x400000  /* address length */
-
-struct pti_tty {
-	struct pti_masterchannel *mc;
-};
-
-struct pti_dev {
-	struct tty_port port[PTITTY_MINOR_NUM];
-	unsigned long pti_addr;
-	unsigned long aperture_base;
-	void __iomem *pti_ioaddr;
-	u8 ia_app[MAX_APP_IDS];
-	u8 ia_os[MAX_OS_IDS];
-	u8 ia_modem[MAX_MODEM_IDS];
-};
-
-/*
- * This protects access to ia_app, ia_os, and ia_modem,
- * which keeps track of channels allocated in
- * an aperture write id.
- */
-static DEFINE_MUTEX(alloclock);
-
-static const struct pci_device_id pci_ids[] = {
-		{PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0x82B)},
-		{0}
-};
-
-static struct tty_driver *pti_tty_driver;
-static struct pti_dev *drv_data;
-
-static unsigned int pti_console_channel;
-static unsigned int pti_control_channel;
-
-/**
- *  pti_write_to_aperture()- The private write function to PTI HW.
- *
- *  @mc: The 'aperture'. It's part of a write address that holds
- *       a master and channel ID.
- *  @buf: Data being written to the HW that will ultimately be seen
- *        in a debugging tool (Fido, Lauterbach).
- *  @len: Size of buffer.
- *
- *  Since each aperture is specified by a unique
- *  master/channel ID, no two processes will be writing
- *  to the same aperture at the same time so no lock is required. The
- *  PTI-Output agent will send these out in the order that they arrived, and
- *  thus, it will intermix these messages. The debug tool can then later
- *  regroup the appropriate message segments together reconstituting each
- *  message.
- */
-static void pti_write_to_aperture(struct pti_masterchannel *mc,
-				  u8 *buf,
-				  int len)
-{
-	int dwordcnt;
-	int final;
-	int i;
-	u32 ptiword;
-	u32 __iomem *aperture;
-	u8 *p = buf;
-
-	/*
-	 * calculate the aperture offset from the base using the master and
-	 * channel id's.
-	 */
-	aperture = drv_data->pti_ioaddr + (mc->master << 15)
-		+ (mc->channel << 8);
-
-	dwordcnt = len >> 2;
-	final = len - (dwordcnt << 2);	    /* final = trailing bytes    */
-	if (final == 0 && dwordcnt != 0) {  /* always need a final dword */
-		final += 4;
-		dwordcnt--;
-	}
-
-	for (i = 0; i < dwordcnt; i++) {
-		ptiword = be32_to_cpu(*(u32 *)p);
-		p += 4;
-		iowrite32(ptiword, aperture);
-	}
-
-	aperture += PTI_LASTDWORD_DTS;	/* adding DTS signals that is EOM */
-
-	ptiword = 0;
-	for (i = 0; i < final; i++)
-		ptiword |= *p++ << (24-(8*i));
-
-	iowrite32(ptiword, aperture);
-	return;
-}
-
-/**
- *  pti_control_frame_built_and_sent()- control frame build and send function.
- *
- *  @mc:          The master / channel structure on which the function
- *                built a control frame.
- *  @thread_name: The thread name associated with the master / channel or
- *                'NULL' if using the 'current' global variable.
- *
- *  To be able to post process the PTI contents on host side, a control frame
- *  is added before sending any PTI content. So the host side knows on
- *  each PTI frame the name of the thread using a dedicated master / channel.
- *  The thread name is retrieved from 'current' global variable if 'thread_name'
- *  is 'NULL', else it is retrieved from 'thread_name' parameter.
- *  This function builds this frame and sends it to a master ID CONTROL_ID.
- *  The overhead is only 32 bytes since the driver only writes to HW
- *  in 32 byte chunks.
- */
-static void pti_control_frame_built_and_sent(struct pti_masterchannel *mc,
-					     const char *thread_name)
-{
-	/*
-	 * Since we access the comm member in current's task_struct, we only
-	 * need to be as large as what 'comm' in that structure is.
-	 */
-	char comm[TASK_COMM_LEN];
-	struct pti_masterchannel mccontrol = {.master = CONTROL_ID,
-					      .channel = 0};
-	const char *thread_name_p;
-	const char *control_format = "%3d %3d %s";
-	u8 control_frame[CONTROL_FRAME_LEN];
-
-	if (!thread_name) {
-		if (!in_interrupt())
-			get_task_comm(comm, current);
-		else
-			strncpy(comm, "Interrupt", TASK_COMM_LEN);
-
-		/* Absolutely ensure our buffer is zero terminated. */
-		comm[TASK_COMM_LEN-1] = 0;
-		thread_name_p = comm;
-	} else {
-		thread_name_p = thread_name;
-	}
-
-	mccontrol.channel = pti_control_channel;
-	pti_control_channel = (pti_control_channel + 1) & 0x7f;
-
-	snprintf(control_frame, CONTROL_FRAME_LEN, control_format, mc->master,
-		mc->channel, thread_name_p);
-	pti_write_to_aperture(&mccontrol, control_frame, strlen(control_frame));
-}
-
-/**
- *  pti_write_full_frame_to_aperture()- high level function to
- *					write to PTI.
- *
- *  @mc:  The 'aperture'. It's part of a write address that holds
- *        a master and channel ID.
- *  @buf: Data being written to the HW that will ultimately be seen
- *        in a debugging tool (Fido, Lauterbach).
- *  @len: Size of buffer.
- *
- *  All threads sending data (either console, user space application, ...)
- *  are calling the high level function to write to PTI meaning that it is
- *  possible to add a control frame before sending the content.
- */
-static void pti_write_full_frame_to_aperture(struct pti_masterchannel *mc,
-						const unsigned char *buf,
-						int len)
-{
-	pti_control_frame_built_and_sent(mc, NULL);
-	pti_write_to_aperture(mc, (u8 *)buf, len);
-}
-
-/**
- * get_id()- Allocate a master and channel ID.
- *
- * @id_array:    an array of bits representing what channel
- *               id's are allocated for writing.
- * @max_ids:     The max amount of available write IDs to use.
- * @base_id:     The starting SW channel ID, based on the Intel
- *               PTI arch.
- * @thread_name: The thread name associated with the master / channel or
- *               'NULL' if using the 'current' global variable.
- *
- * Returns:
- *	pti_masterchannel struct with master, channel ID address
- *	0 for error
- *
- * Each bit in the arrays ia_app and ia_os correspond to a master and
- * channel id. The bit is one if the id is taken and 0 if free. For
- * every master there are 128 channel id's.
- */
-static struct pti_masterchannel *get_id(u8 *id_array,
-					int max_ids,
-					int base_id,
-					const char *thread_name)
-{
-	struct pti_masterchannel *mc;
-	int i, j, mask;
-
-	mc = kmalloc(sizeof(struct pti_masterchannel), GFP_KERNEL);
-	if (mc == NULL)
-		return NULL;
-
-	/* look for a byte with a free bit */
-	for (i = 0; i < max_ids; i++)
-		if (id_array[i] != 0xff)
-			break;
-	if (i == max_ids) {
-		kfree(mc);
-		return NULL;
-	}
-	/* find the bit in the 128 possible channel opportunities */
-	mask = 0x80;
-	for (j = 0; j < 8; j++) {
-		if ((id_array[i] & mask) == 0)
-			break;
-		mask >>= 1;
-	}
-
-	/* grab it */
-	id_array[i] |= mask;
-	mc->master  = base_id;
-	mc->channel = ((i & 0xf)<<3) + j;
-	/* write new master Id / channel Id allocation to channel control */
-	pti_control_frame_built_and_sent(mc, thread_name);
-	return mc;
-}
-
-/*
- * The following three functions:
- * pti_request_mastercahannel(), mipi_release_masterchannel()
- * and pti_writedata() are an API for other kernel drivers to
- * access PTI.
- */
-
-/**
- * pti_request_masterchannel()- Kernel API function used to allocate
- *				a master, channel ID address
- *				to write to PTI HW.
- *
- * @type:        0- request Application  master, channel aperture ID
- *                  write address.
- *               1- request OS master, channel aperture ID write
- *                  address.
- *               2- request Modem master, channel aperture ID
- *                  write address.
- *               Other values, error.
- * @thread_name: The thread name associated with the master / channel or
- *               'NULL' if using the 'current' global variable.
- *
- * Returns:
- *	pti_masterchannel struct
- *	0 for error
- */
-struct pti_masterchannel *pti_request_masterchannel(u8 type,
-						    const char *thread_name)
-{
-	struct pti_masterchannel *mc;
-
-	mutex_lock(&alloclock);
-
-	switch (type) {
-
-	case 0:
-		mc = get_id(drv_data->ia_app, MAX_APP_IDS,
-			    APP_BASE_ID, thread_name);
-		break;
-
-	case 1:
-		mc = get_id(drv_data->ia_os, MAX_OS_IDS,
-			    OS_BASE_ID, thread_name);
-		break;
-
-	case 2:
-		mc = get_id(drv_data->ia_modem, MAX_MODEM_IDS,
-			    MODEM_BASE_ID, thread_name);
-		break;
-	default:
-		mc = NULL;
-	}
-
-	mutex_unlock(&alloclock);
-	return mc;
-}
-EXPORT_SYMBOL_GPL(pti_request_masterchannel);
-
-/**
- * pti_release_masterchannel()- Kernel API function used to release
- *				a master, channel ID address
- *				used to write to PTI HW.
- *
- * @mc: master, channel apeture ID address to be released.  This
- *      will de-allocate the structure via kfree().
- */
-void pti_release_masterchannel(struct pti_masterchannel *mc)
-{
-	u8 master, channel, i;
-
-	mutex_lock(&alloclock);
-
-	if (mc) {
-		master = mc->master;
-		channel = mc->channel;
-
-		if (master == APP_BASE_ID) {
-			i = channel >> 3;
-			drv_data->ia_app[i] &=  ~(0x80>>(channel & 0x7));
-		} else if (master == OS_BASE_ID) {
-			i = channel >> 3;
-			drv_data->ia_os[i] &= ~(0x80>>(channel & 0x7));
-		} else {
-			i = channel >> 3;
-			drv_data->ia_modem[i] &= ~(0x80>>(channel & 0x7));
-		}
-
-		kfree(mc);
-	}
-
-	mutex_unlock(&alloclock);
-}
-EXPORT_SYMBOL_GPL(pti_release_masterchannel);
-
-/**
- * pti_writedata()- Kernel API function used to write trace
- *                  debugging data to PTI HW.
- *
- * @mc:    Master, channel aperture ID address to write to.
- *         Null value will return with no write occurring.
- * @buf:   Trace debuging data to write to the PTI HW.
- *         Null value will return with no write occurring.
- * @count: Size of buf. Value of 0 or a negative number will
- *         return with no write occuring.
- */
-void pti_writedata(struct pti_masterchannel *mc, u8 *buf, int count)
-{
-	/*
-	 * since this function is exported, this is treated like an
-	 * API function, thus, all parameters should
-	 * be checked for validity.
-	 */
-	if ((mc != NULL) && (buf != NULL) && (count > 0))
-		pti_write_to_aperture(mc, buf, count);
-	return;
-}
-EXPORT_SYMBOL_GPL(pti_writedata);
-
-/*
- * for the tty_driver_*() basic function descriptions, see tty_driver.h.
- * Specific header comments made for PTI-related specifics.
- */
-
-/**
- * pti_tty_driver_open()- Open an Application master, channel aperture
- * ID to the PTI device via tty device.
- *
- * @tty: tty interface.
- * @filp: filp interface pased to tty_port_open() call.
- *
- * Returns:
- *	int, 0 for success
- *	otherwise, fail value
- *
- * The main purpose of using the tty device interface is for
- * each tty port to have a unique PTI write aperture.  In an
- * example use case, ttyPTI0 gets syslogd and an APP aperture
- * ID and ttyPTI1 is where the n_tracesink ldisc hooks to route
- * modem messages into PTI.  Modem trace data does not have to
- * go to ttyPTI1, but ttyPTI0 and ttyPTI1 do need to be distinct
- * master IDs.  These messages go through the PTI HW and out of
- * the handheld platform and to the Fido/Lauterbach device.
- */
-static int pti_tty_driver_open(struct tty_struct *tty, struct file *filp)
-{
-	/*
-	 * we actually want to allocate a new channel per open, per
-	 * system arch.  HW gives more than plenty channels for a single
-	 * system task to have its own channel to write trace data. This
-	 * also removes a locking requirement for the actual write
-	 * procedure.
-	 */
-	return tty_port_open(tty->port, tty, filp);
-}
-
-/**
- * pti_tty_driver_close()- close tty device and release Application
- * master, channel aperture ID to the PTI device via tty device.
- *
- * @tty: tty interface.
- * @filp: filp interface pased to tty_port_close() call.
- *
- * The main purpose of using the tty device interface is to route
- * syslog daemon messages to the PTI HW and out of the handheld platform
- * and to the Fido/Lauterbach device.
- */
-static void pti_tty_driver_close(struct tty_struct *tty, struct file *filp)
-{
-	tty_port_close(tty->port, tty, filp);
-}
-
-/**
- * pti_tty_install()- Used to set up specific master-channels
- *		      to tty ports for organizational purposes when
- *		      tracing viewed from debuging tools.
- *
- * @driver: tty driver information.
- * @tty: tty struct containing pti information.
- *
- * Returns:
- *	0 for success
- *	otherwise, error
- */
-static int pti_tty_install(struct tty_driver *driver, struct tty_struct *tty)
-{
-	int idx = tty->index;
-	struct pti_tty *pti_tty_data;
-	int ret = tty_standard_install(driver, tty);
-
-	if (ret == 0) {
-		pti_tty_data = kmalloc(sizeof(struct pti_tty), GFP_KERNEL);
-		if (pti_tty_data == NULL)
-			return -ENOMEM;
-
-		if (idx == PTITTY_MINOR_START)
-			pti_tty_data->mc = pti_request_masterchannel(0, NULL);
-		else
-			pti_tty_data->mc = pti_request_masterchannel(2, NULL);
-
-		if (pti_tty_data->mc == NULL) {
-			kfree(pti_tty_data);
-			return -ENXIO;
-		}
-		tty->driver_data = pti_tty_data;
-	}
-
-	return ret;
-}
-
-/**
- * pti_tty_cleanup()- Used to de-allocate master-channel resources
- *		      tied to tty's of this driver.
- *
- * @tty: tty struct containing pti information.
- */
-static void pti_tty_cleanup(struct tty_struct *tty)
-{
-	struct pti_tty *pti_tty_data = tty->driver_data;
-	if (pti_tty_data == NULL)
-		return;
-	pti_release_masterchannel(pti_tty_data->mc);
-	kfree(pti_tty_data);
-	tty->driver_data = NULL;
-}
-
-/**
- * pti_tty_driver_write()-  Write trace debugging data through the char
- * interface to the PTI HW.  Part of the misc device implementation.
- *
- * @tty: tty struct containing pti information.
- * @buf: trace data to be written.
- * @len:  # of byte to write.
- *
- * Returns:
- *	int, # of bytes written
- *	otherwise, error
- */
-static int pti_tty_driver_write(struct tty_struct *tty,
-	const unsigned char *buf, int len)
-{
-	struct pti_tty *pti_tty_data = tty->driver_data;
-	if ((pti_tty_data != NULL) && (pti_tty_data->mc != NULL)) {
-		pti_write_to_aperture(pti_tty_data->mc, (u8 *)buf, len);
-		return len;
-	}
-	/*
-	 * we can't write to the pti hardware if the private driver_data
-	 * and the mc address is not there.
-	 */
-	else
-		return -EFAULT;
-}
-
-/**
- * pti_tty_write_room()- Always returns 2048.
- *
- * @tty: contains tty info of the pti driver.
- */
-static int pti_tty_write_room(struct tty_struct *tty)
-{
-	return 2048;
-}
-
-/**
- * pti_char_open()- Open an Application master, channel aperture
- * ID to the PTI device. Part of the misc device implementation.
- *
- * @inode: not used.
- * @filp:  Output- will have a masterchannel struct set containing
- *                 the allocated application PTI aperture write address.
- *
- * Returns:
- *	int, 0 for success
- *	otherwise, a fail value
- */
-static int pti_char_open(struct inode *inode, struct file *filp)
-{
-	struct pti_masterchannel *mc;
-
-	/*
-	 * We really do want to fail immediately if
-	 * pti_request_masterchannel() fails,
-	 * before assigning the value to filp->private_data.
-	 * Slightly easier to debug if this driver needs debugging.
-	 */
-	mc = pti_request_masterchannel(0, NULL);
-	if (mc == NULL)
-		return -ENOMEM;
-	filp->private_data = mc;
-	return 0;
-}
-
-/**
- * pti_char_release()-  Close a char channel to the PTI device. Part
- * of the misc device implementation.
- *
- * @inode: Not used in this implementaiton.
- * @filp:  Contains private_data that contains the master, channel
- *         ID to be released by the PTI device.
- *
- * Returns:
- *	always 0
- */
-static int pti_char_release(struct inode *inode, struct file *filp)
-{
-	pti_release_masterchannel(filp->private_data);
-	filp->private_data = NULL;
-	return 0;
-}
-
-/**
- * pti_char_write()-  Write trace debugging data through the char
- * interface to the PTI HW.  Part of the misc device implementation.
- *
- * @filp:  Contains private data which is used to obtain
- *         master, channel write ID.
- * @data:  trace data to be written.
- * @len:   # of byte to write.
- * @ppose: Not used in this function implementation.
- *
- * Returns:
- *	int, # of bytes written
- *	otherwise, error value
- *
- * Notes: From side discussions with Alan Cox and experimenting
- * with PTI debug HW like Nokia's Fido box and Lauterbach
- * devices, 8192 byte write buffer used by USER_COPY_SIZE was
- * deemed an appropriate size for this type of usage with
- * debugging HW.
- */
-static ssize_t pti_char_write(struct file *filp, const char __user *data,
-			      size_t len, loff_t *ppose)
-{
-	struct pti_masterchannel *mc;
-	void *kbuf;
-	const char __user *tmp;
-	size_t size = USER_COPY_SIZE;
-	size_t n = 0;
-
-	tmp = data;
-	mc = filp->private_data;
-
-	kbuf = kmalloc(size, GFP_KERNEL);
-	if (kbuf == NULL)  {
-		pr_err("%s(%d): buf allocation failed\n",
-			__func__, __LINE__);
-		return -ENOMEM;
-	}
-
-	do {
-		if (len - n > USER_COPY_SIZE)
-			size = USER_COPY_SIZE;
-		else
-			size = len - n;
-
-		if (copy_from_user(kbuf, tmp, size)) {
-			kfree(kbuf);
-			return n ? n : -EFAULT;
-		}
-
-		pti_write_to_aperture(mc, kbuf, size);
-		n  += size;
-		tmp += size;
-
-	} while (len > n);
-
-	kfree(kbuf);
-	return len;
-}
-
-static const struct tty_operations pti_tty_driver_ops = {
-	.open		= pti_tty_driver_open,
-	.close		= pti_tty_driver_close,
-	.write		= pti_tty_driver_write,
-	.write_room	= pti_tty_write_room,
-	.install	= pti_tty_install,
-	.cleanup	= pti_tty_cleanup
-};
-
-static const struct file_operations pti_char_driver_ops = {
-	.owner		= THIS_MODULE,
-	.write		= pti_char_write,
-	.open		= pti_char_open,
-	.release	= pti_char_release,
-};
-
-static struct miscdevice pti_char_driver = {
-	.minor		= MISC_DYNAMIC_MINOR,
-	.name		= CHARNAME,
-	.fops		= &pti_char_driver_ops
-};
-
-/**
- * pti_console_write()-  Write to the console that has been acquired.
- *
- * @c:   Not used in this implementaiton.
- * @buf: Data to be written.
- * @len: Length of buf.
- */
-static void pti_console_write(struct console *c, const char *buf, unsigned len)
-{
-	static struct pti_masterchannel mc = {.master  = CONSOLE_ID,
-					      .channel = 0};
-
-	mc.channel = pti_console_channel;
-	pti_console_channel = (pti_console_channel + 1) & 0x7f;
-
-	pti_write_full_frame_to_aperture(&mc, buf, len);
-}
-
-/**
- * pti_console_device()-  Return the driver tty structure and set the
- *			  associated index implementation.
- *
- * @c:     Console device of the driver.
- * @index: index associated with c.
- *
- * Returns:
- *	always value of pti_tty_driver structure when this function
- *	is called.
- */
-static struct tty_driver *pti_console_device(struct console *c, int *index)
-{
-	*index = c->index;
-	return pti_tty_driver;
-}
-
-/**
- * pti_console_setup()-  Initialize console variables used by the driver.
- *
- * @c:     Not used.
- * @opts:  Not used.
- *
- * Returns:
- *	always 0.
- */
-static int pti_console_setup(struct console *c, char *opts)
-{
-	pti_console_channel = 0;
-	pti_control_channel = 0;
-	return 0;
-}
-
-/*
- * pti_console struct, used to capture OS printk()'s and shift
- * out to the PTI device for debugging.  This cannot be
- * enabled upon boot because of the possibility of eating
- * any serial console printk's (race condition discovered).
- * The console should be enabled upon when the tty port is
- * used for the first time.  Since the primary purpose for
- * the tty port is to hook up syslog to it, the tty port
- * will be open for a really long time.
- */
-static struct console pti_console = {
-	.name		= TTYNAME,
-	.write		= pti_console_write,
-	.device		= pti_console_device,
-	.setup		= pti_console_setup,
-	.flags		= CON_PRINTBUFFER,
-	.index		= 0,
-};
-
-/**
- * pti_port_activate()- Used to start/initialize any items upon
- * first opening of tty_port().
- *
- * @port: The tty port number of the PTI device.
- * @tty:  The tty struct associated with this device.
- *
- * Returns:
- *	always returns 0
- *
- * Notes: The primary purpose of the PTI tty port 0 is to hook
- * the syslog daemon to it; thus this port will be open for a
- * very long time.
- */
-static int pti_port_activate(struct tty_port *port, struct tty_struct *tty)
-{
-	if (port->tty->index == PTITTY_MINOR_START)
-		console_start(&pti_console);
-	return 0;
-}
-
-/**
- * pti_port_shutdown()- Used to stop/shutdown any items upon the
- * last tty port close.
- *
- * @port: The tty port number of the PTI device.
- *
- * Notes: The primary purpose of the PTI tty port 0 is to hook
- * the syslog daemon to it; thus this port will be open for a
- * very long time.
- */
-static void pti_port_shutdown(struct tty_port *port)
-{
-	if (port->tty->index == PTITTY_MINOR_START)
-		console_stop(&pti_console);
-}
-
-static const struct tty_port_operations tty_port_ops = {
-	.activate = pti_port_activate,
-	.shutdown = pti_port_shutdown,
-};
-
-/*
- * Note the _probe() call sets everything up and ties the char and tty
- * to successfully detecting the PTI device on the pci bus.
- */
-
-/**
- * pti_pci_probe()- Used to detect pti on the pci bus and set
- *		    things up in the driver.
- *
- * @pdev: pci_dev struct values for pti.
- * @ent:  pci_device_id struct for pti driver.
- *
- * Returns:
- *	0 for success
- *	otherwise, error
- */
-static int pti_pci_probe(struct pci_dev *pdev,
-		const struct pci_device_id *ent)
-{
-	unsigned int a;
-	int retval;
-	int pci_bar = 1;
-
-	dev_dbg(&pdev->dev, "%s %s(%d): PTI PCI ID %04x:%04x\n", __FILE__,
-			__func__, __LINE__, pdev->vendor, pdev->device);
-
-	retval = misc_register(&pti_char_driver);
-	if (retval) {
-		pr_err("%s(%d): CHAR registration failed of pti driver\n",
-			__func__, __LINE__);
-		pr_err("%s(%d): Error value returned: %d\n",
-			__func__, __LINE__, retval);
-		goto err;
-	}
-
-	retval = pci_enable_device(pdev);
-	if (retval != 0) {
-		dev_err(&pdev->dev,
-			"%s: pci_enable_device() returned error %d\n",
-			__func__, retval);
-		goto err_unreg_misc;
-	}
-
-	drv_data = kzalloc(sizeof(*drv_data), GFP_KERNEL);
-	if (drv_data == NULL) {
-		retval = -ENOMEM;
-		dev_err(&pdev->dev,
-			"%s(%d): kmalloc() returned NULL memory.\n",
-			__func__, __LINE__);
-		goto err_disable_pci;
-	}
-	drv_data->pti_addr = pci_resource_start(pdev, pci_bar);
-
-	retval = pci_request_region(pdev, pci_bar, dev_name(&pdev->dev));
-	if (retval != 0) {
-		dev_err(&pdev->dev,
-			"%s(%d): pci_request_region() returned error %d\n",
-			__func__, __LINE__, retval);
-		goto err_free_dd;
-	}
-	drv_data->aperture_base = drv_data->pti_addr+APERTURE_14;
-	drv_data->pti_ioaddr =
-		ioremap((u32)drv_data->aperture_base,
-		APERTURE_LEN);
-	if (!drv_data->pti_ioaddr) {
-		retval = -ENOMEM;
-		goto err_rel_reg;
-	}
-
-	pci_set_drvdata(pdev, drv_data);
-
-	for (a = 0; a < PTITTY_MINOR_NUM; a++) {
-		struct tty_port *port = &drv_data->port[a];
-		tty_port_init(port);
-		port->ops = &tty_port_ops;
-
-		tty_port_register_device(port, pti_tty_driver, a, &pdev->dev);
-	}
-
-	register_console(&pti_console);
-
-	return 0;
-err_rel_reg:
-	pci_release_region(pdev, pci_bar);
-err_free_dd:
-	kfree(drv_data);
-err_disable_pci:
-	pci_disable_device(pdev);
-err_unreg_misc:
-	misc_deregister(&pti_char_driver);
-err:
-	return retval;
-}
-
-/**
- * pti_pci_remove()- Driver exit method to remove PTI from
- *		   PCI bus.
- * @pdev: variable containing pci info of PTI.
- */
-static void pti_pci_remove(struct pci_dev *pdev)
-{
-	struct pti_dev *drv_data = pci_get_drvdata(pdev);
-	unsigned int a;
-
-	unregister_console(&pti_console);
-
-	for (a = 0; a < PTITTY_MINOR_NUM; a++) {
-		tty_unregister_device(pti_tty_driver, a);
-		tty_port_destroy(&drv_data->port[a]);
-	}
-
-	iounmap(drv_data->pti_ioaddr);
-	kfree(drv_data);
-	pci_release_region(pdev, 1);
-	pci_disable_device(pdev);
-
-	misc_deregister(&pti_char_driver);
-}
-
-static struct pci_driver pti_pci_driver = {
-	.name		= PCINAME,
-	.id_table	= pci_ids,
-	.probe		= pti_pci_probe,
-	.remove		= pti_pci_remove,
-};
-
-/**
- * pti_init()- Overall entry/init call to the pti driver.
- *             It starts the registration process with the kernel.
- *
- * Returns:
- *	int __init, 0 for success
- *	otherwise value is an error
- *
- */
-static int __init pti_init(void)
-{
-	int retval;
-
-	/* First register module as tty device */
-
-	pti_tty_driver = alloc_tty_driver(PTITTY_MINOR_NUM);
-	if (pti_tty_driver == NULL) {
-		pr_err("%s(%d): Memory allocation failed for ptiTTY driver\n",
-			__func__, __LINE__);
-		return -ENOMEM;
-	}
-
-	pti_tty_driver->driver_name		= DRIVERNAME;
-	pti_tty_driver->name			= TTYNAME;
-	pti_tty_driver->major			= 0;
-	pti_tty_driver->minor_start		= PTITTY_MINOR_START;
-	pti_tty_driver->type			= TTY_DRIVER_TYPE_SYSTEM;
-	pti_tty_driver->subtype			= SYSTEM_TYPE_SYSCONS;
-	pti_tty_driver->flags			= TTY_DRIVER_REAL_RAW |
-						  TTY_DRIVER_DYNAMIC_DEV;
-	pti_tty_driver->init_termios		= tty_std_termios;
-
-	tty_set_operations(pti_tty_driver, &pti_tty_driver_ops);
-
-	retval = tty_register_driver(pti_tty_driver);
-	if (retval) {
-		pr_err("%s(%d): TTY registration failed of pti driver\n",
-			__func__, __LINE__);
-		pr_err("%s(%d): Error value returned: %d\n",
-			__func__, __LINE__, retval);
-
-		goto put_tty;
-	}
-
-	retval = pci_register_driver(&pti_pci_driver);
-	if (retval) {
-		pr_err("%s(%d): PCI registration failed of pti driver\n",
-			__func__, __LINE__);
-		pr_err("%s(%d): Error value returned: %d\n",
-			__func__, __LINE__, retval);
-		goto unreg_tty;
-	}
-
-	return 0;
-unreg_tty:
-	tty_unregister_driver(pti_tty_driver);
-put_tty:
-	put_tty_driver(pti_tty_driver);
-	pti_tty_driver = NULL;
-	return retval;
-}
-
-/**
- * pti_exit()- Unregisters this module as a tty and pci driver.
- */
-static void __exit pti_exit(void)
-{
-	tty_unregister_driver(pti_tty_driver);
-	pci_unregister_driver(&pti_pci_driver);
-	put_tty_driver(pti_tty_driver);
-}
-
-module_init(pti_init);
-module_exit(pti_exit);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Ken Mills, Jay Freyensee");
-MODULE_DESCRIPTION("PTI Driver");
-

drivers/tty/Makefile

···
 obj-$(CONFIG_MAGIC_SYSRQ)	+= sysrq.o
 obj-$(CONFIG_N_HDLC)		+= n_hdlc.o
 obj-$(CONFIG_N_GSM)		+= n_gsm.o
-obj-$(CONFIG_TRACE_ROUTER)	+= n_tracerouter.o
-obj-$(CONFIG_TRACE_SINK)	+= n_tracesink.o
 obj-$(CONFIG_R3964)		+= n_r3964.o
 
 obj-y				+= vt/

drivers/tty/n_tracerouter.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- *  n_tracerouter.c - Trace data router through tty space
- *
- *  Copyright (C) Intel 2011
- *
- * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- *
- * This trace router uses the Linux line discipline framework to route
- * trace data coming from a HW Modem to a PTI (Parallel Trace Module) port.
- * The solution is not specific to a HW modem and this line disciple can
- * be used to route any stream of data in kernel space.
- * This is part of a solution for the P1149.7, compact JTAG, standard.
- */
-
-#include <linux/init.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/types.h>
-#include <linux/ioctl.h>
-#include <linux/tty.h>
-#include <linux/tty_ldisc.h>
-#include <linux/errno.h>
-#include <linux/string.h>
-#include <linux/mutex.h>
-#include <linux/slab.h>
-#include <linux/bug.h>
-#include "n_tracesink.h"
-
-/*
- * Other ldisc drivers use 65536 which basically means,
- * 'I can always accept 64k' and flow control is off.
- * This number is deemed appropriate for this driver.
- */
-#define RECEIVE_ROOM	65536
-#define DRIVERNAME	"n_tracerouter"
-
-/*
- * struct to hold private configuration data for this ldisc.
- * opencalled is used to hold if this ldisc has been opened.
- * kref_tty holds the tty reference the ldisc sits on top of.
- */
-struct tracerouter_data {
-	u8 opencalled;
-	struct tty_struct *kref_tty;
-};
-static struct tracerouter_data *tr_data;
-
-/* lock for when tty reference is being used */
-static DEFINE_MUTEX(routelock);
-
-/**
- * n_tracerouter_open() - Called when a tty is opened by a SW entity.
- * @tty: terminal device to the ldisc.
- *
- * Return:
- *      0 for success.
- *
- * Caveats: This should only be opened one time per SW entity.
- */
-static int n_tracerouter_open(struct tty_struct *tty)
-{
-	int retval = -EEXIST;
-
-	mutex_lock(&routelock);
-	if (tr_data->opencalled == 0) {
-
-		tr_data->kref_tty = tty_kref_get(tty);
-		if (tr_data->kref_tty == NULL) {
-			retval = -EFAULT;
-		} else {
-			tr_data->opencalled = 1;
-			tty->disc_data      = tr_data;
-			tty->receive_room   = RECEIVE_ROOM;
-			tty_driver_flush_buffer(tty);
-			retval = 0;
-		}
-	}
-	mutex_unlock(&routelock);
-	return retval;
-}
-
-/**
- * n_tracerouter_close() - close connection
- * @tty: terminal device to the ldisc.
- *
- * Called when a software entity wants to close a connection.
- */
-static void n_tracerouter_close(struct tty_struct *tty)
-{
-	struct tracerouter_data *tptr = tty->disc_data;
-
-	mutex_lock(&routelock);
-	WARN_ON(tptr->kref_tty != tr_data->kref_tty);
-	tty_driver_flush_buffer(tty);
-	tty_kref_put(tr_data->kref_tty);
-	tr_data->kref_tty = NULL;
-	tr_data->opencalled = 0;
-	tty->disc_data = NULL;
-	mutex_unlock(&routelock);
-}
-
-/**
- * n_tracerouter_read() - read request from user space
- * @tty:  terminal device passed into the ldisc.
- * @file: pointer to open file object.
- * @buf:  pointer to the data buffer that gets eventually returned.
- * @nr:   number of bytes of the data buffer that is returned.
- *
- * function that allows read() functionality in userspace. By default if this
- * is not implemented it returns -EIO. This module is functioning like a
- * router via n_tracerouter_receivebuf(), and there is no real requirement
- * to implement this function. However, an error return value other than
- * -EIO should be used just to show that there was an intent not to have
- * this function implemented.  Return value based on read() man pages.
- *
- * Return:
- *	 -EINVAL
- */
-static ssize_t n_tracerouter_read(struct tty_struct *tty, struct file *file,
-				  unsigned char __user *buf, size_t nr) {
-	return -EINVAL;
-}
-
-/**
- * n_tracerouter_write() - Function that allows write() in userspace.
- * @tty:  terminal device passed into the ldisc.
- * @file: pointer to open file object.
- * @buf:  pointer to the data buffer that gets eventually returned.
- * @nr:   number of bytes of the data buffer that is returned.
- *
- * By default if this is not implemented, it returns -EIO.
- * This should not be implemented, ever, because
- * 1. this driver is functioning like a router via
- *    n_tracerouter_receivebuf()
- * 2. No writes to HW will ever go through this line discpline driver.
- * However, an error return value other than -EIO should be used
- * just to show that there was an intent not to have this function
- * implemented.  Return value based on write() man pages.
- *
- * Return:
- *	-EINVAL
- */
-static ssize_t n_tracerouter_write(struct tty_struct *tty, struct file *file,
-				   const unsigned char *buf, size_t nr) {
-	return -EINVAL;
-}
-
-/**
- * n_tracerouter_receivebuf() - Routing function for driver.
- * @tty: terminal device passed into the ldisc.  It's assumed
- *       tty will never be NULL.
- * @cp:  buffer, block of characters to be eventually read by
- *       someone, somewhere (user read() call or some kernel function).
- * @fp:  flag buffer.
- * @count: number of characters (aka, bytes) in cp.
- *
- * This function takes the input buffer, cp, and passes it to
- * an external API function for processing.
- */
-static void n_tracerouter_receivebuf(struct tty_struct *tty,
-					const unsigned char *cp,
-					char *fp, int count)
-{
-	mutex_lock(&routelock);
-	n_tracesink_datadrain((u8 *) cp, count);
-	mutex_unlock(&routelock);
-}
-
-/*
- * Flush buffer is not impelemented as the ldisc has no internal buffering
- * so the tty_driver_flush_buffer() is sufficient for this driver's needs.
- */
-
-static struct tty_ldisc_ops tty_ptirouter_ldisc = {
-	.owner		= THIS_MODULE,
-	.magic		= TTY_LDISC_MAGIC,
-	.name		= DRIVERNAME,
-	.open		= n_tracerouter_open,
-	.close		= n_tracerouter_close,
-	.read		= n_tracerouter_read,
-	.write		= n_tracerouter_write,
-	.receive_buf	= n_tracerouter_receivebuf
-};
-
-/**
- * n_tracerouter_init -	module initialisation
- *
- * Registers this module as a line discipline driver.
- *
- * Return:
- *	0 for success, any other value error.
- */
-static int __init n_tracerouter_init(void)
-{
-	int retval;
-
-	tr_data = kzalloc(sizeof(struct tracerouter_data), GFP_KERNEL);
-	if (tr_data == NULL)
-		return -ENOMEM;
-
-
-	/* Note N_TRACEROUTER is defined in linux/tty.h */
-	retval = tty_register_ldisc(N_TRACEROUTER, &tty_ptirouter_ldisc);
-	if (retval < 0) {
-		pr_err("%s: Registration failed: %d\n", __func__, retval);
-		kfree(tr_data);
-	}
-	return retval;
-}
-
-/**
- * n_tracerouter_exit -	module unload
- *
- * Removes this module as a line discipline driver.
- */
-static void __exit n_tracerouter_exit(void)
-{
-	int retval = tty_unregister_ldisc(N_TRACEROUTER);
-
-	if (retval < 0)
-		pr_err("%s: Unregistration failed: %d\n", __func__,  retval);
-	else
-		kfree(tr_data);
-}
-
-module_init(n_tracerouter_init);
-module_exit(n_tracerouter_exit);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Jay Freyensee");
-MODULE_ALIAS_LDISC(N_TRACEROUTER);
-MODULE_DESCRIPTION("Trace router ldisc driver");

drivers/tty/n_tracesink.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- *  n_tracesink.c - Trace data router and sink path through tty space.
- *
- *  Copyright (C) Intel 2011
- *
- * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- *
- * The trace sink uses the Linux line discipline framework to receive
- * trace data coming from the PTI source line discipline driver
- * to a user-desired tty port, like USB.
- * This is to provide a way to extract modem trace data on
- * devices that do not have a PTI HW module, or just need modem
- * trace data to come out of a different HW output port.
- * This is part of a solution for the P1149.7, compact JTAG, standard.
- */
-
-#include <linux/init.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/types.h>
-#include <linux/ioctl.h>
-#include <linux/tty.h>
-#include <linux/tty_ldisc.h>
-#include <linux/errno.h>
-#include <linux/string.h>
-#include <linux/bug.h>
-#include "n_tracesink.h"
-
-/*
- * Other ldisc drivers use 65536 which basically means,
- * 'I can always accept 64k' and flow control is off.
- * This number is deemed appropriate for this driver.
- */
-#define RECEIVE_ROOM	65536
-#define DRIVERNAME	"n_tracesink"
-
-/*
- * there is a quirk with this ldisc is he can write data
- * to a tty from anyone calling his kernel API, which
- * meets customer requirements in the drivers/misc/pti.c
- * project.  So he needs to know when he can and cannot write when
- * the API is called. In theory, the API can be called
- * after an init() but before a successful open() which
- * would crash the system if tty is not checked.
- */
-static struct tty_struct *this_tty;
-static DEFINE_MUTEX(writelock);
-
-/**
- * n_tracesink_open() - Called when a tty is opened by a SW entity.
- * @tty: terminal device to the ldisc.
- *
- * Return:
- *      0 for success,
- *      -EFAULT = couldn't get a tty kref n_tracesink will sit
- *       on top of
- *      -EEXIST = open() called successfully once and it cannot
- *      be called again.
- *
- * Caveats: open() should only be successful the first time a
- * SW entity calls it.
- */
-static int n_tracesink_open(struct tty_struct *tty)
-{
-	int retval = -EEXIST;
-
-	mutex_lock(&writelock);
-	if (this_tty == NULL) {
-		this_tty = tty_kref_get(tty);
-		if (this_tty == NULL) {
-			retval = -EFAULT;
-		} else {
-			tty->disc_data = this_tty;
-			tty_driver_flush_buffer(tty);
-			retval = 0;
-		}
-	}
-	mutex_unlock(&writelock);
-
-	return retval;
-}
-
-/**
- * n_tracesink_close() - close connection
- * @tty: terminal device to the ldisc.
- *
- * Called when a software entity wants to close a connection.
- */
-static void n_tracesink_close(struct tty_struct *tty)
-{
-	mutex_lock(&writelock);
-	tty_driver_flush_buffer(tty);
-	tty_kref_put(this_tty);
-	this_tty = NULL;
-	tty->disc_data = NULL;
-	mutex_unlock(&writelock);
-}
-
-/**
- * n_tracesink_read() - read request from user space
- * @tty:  terminal device passed into the ldisc.
- * @file: pointer to open file object.
- * @buf:  pointer to the data buffer that gets eventually returned.
- * @nr:   number of bytes of the data buffer that is returned.
- *
- * function that allows read() functionality in userspace. By default if this
- * is not implemented it returns -EIO. This module is functioning like a
- * router via n_tracesink_receivebuf(), and there is no real requirement
- * to implement this function. However, an error return value other than
- * -EIO should be used just to show that there was an intent not to have
- * this function implemented.  Return value based on read() man pages.
- *
- * Return:
- *	 -EINVAL
- */
-static ssize_t n_tracesink_read(struct tty_struct *tty, struct file *file,
-				unsigned char __user *buf, size_t nr) {
-	return -EINVAL;
-}
-
-/**
- * n_tracesink_write() - Function that allows write() in userspace.
- * @tty:  terminal device passed into the ldisc.
- * @file: pointer to open file object.
- * @buf:  pointer to the data buffer that gets eventually returned.
- * @nr:   number of bytes of the data buffer that is returned.
- *
- * By default if this is not implemented, it returns -EIO.
- * This should not be implemented, ever, because
- * 1. this driver is functioning like a router via
- *    n_tracesink_receivebuf()
- * 2. No writes to HW will ever go through this line discpline driver.
- * However, an error return value other than -EIO should be used
- * just to show that there was an intent not to have this function
- * implemented.  Return value based on write() man pages.
- *
- * Return:
- *	-EINVAL
- */
-static ssize_t n_tracesink_write(struct tty_struct *tty, struct file *file,
-				 const unsigned char *buf, size_t nr) {
-	return -EINVAL;
-}
-
-/**
- * n_tracesink_datadrain() - Kernel API function used to route
- *			     trace debugging data to user-defined
- *			     port like USB.
- *
- * @buf:   Trace debuging data buffer to write to tty target
- *         port. Null value will return with no write occurring.
- * @count: Size of buf. Value of 0 or a negative number will
- *         return with no write occuring.
- *
- * Caveat: If this line discipline does not set the tty it sits
- * on top of via an open() call, this API function will not
- * call the tty's write() call because it will have no pointer
- * to call the write().
- */
-void n_tracesink_datadrain(u8 *buf, int count)
-{
-	mutex_lock(&writelock);
-
-	if ((buf != NULL) && (count > 0) && (this_tty != NULL))
-		this_tty->ops->write(this_tty, buf, count);
-
-	mutex_unlock(&writelock);
-}
-EXPORT_SYMBOL_GPL(n_tracesink_datadrain);
-
-/*
- * Flush buffer is not impelemented as the ldisc has no internal buffering
- * so the tty_driver_flush_buffer() is sufficient for this driver's needs.
- */
-
-/*
- * tty_ldisc function operations for this driver.
- */
-static struct tty_ldisc_ops tty_n_tracesink = {
-	.owner		= THIS_MODULE,
-	.magic		= TTY_LDISC_MAGIC,
-	.name		= DRIVERNAME,
-	.open		= n_tracesink_open,
-	.close		= n_tracesink_close,
-	.read		= n_tracesink_read,
-	.write		= n_tracesink_write
-};
-
-/**
- * n_tracesink_init-	module initialisation
- *
- * Registers this module as a line discipline driver.
- *
- * Return:
- *	0 for success, any other value error.
- */
-static int __init n_tracesink_init(void)
-{
-	/* Note N_TRACESINK is defined in linux/tty.h */
-	int retval = tty_register_ldisc(N_TRACESINK, &tty_n_tracesink);
-
-	if (retval < 0)
-		pr_err("%s: Registration failed: %d\n", __func__, retval);
-
-	return retval;
-}
-
-/**
- * n_tracesink_exit -	module unload
- *
- * Removes this module as a line discipline driver.
- */
-static void __exit n_tracesink_exit(void)
-{
-	int retval = tty_unregister_ldisc(N_TRACESINK);
-
-	if (retval < 0)
-		pr_err("%s: Unregistration failed: %d\n", __func__,  retval);
-}
-
-module_init(n_tracesink_init);
-module_exit(n_tracesink_exit);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Jay Freyensee");
-MODULE_ALIAS_LDISC(N_TRACESINK);
-MODULE_DESCRIPTION("Trace sink ldisc driver");

drivers/tty/n_tracesink.h

···
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- *  n_tracesink.h - Kernel driver API to route trace data in kernel space.
- *
- *  Copyright (C) Intel 2011
- *
- * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- *
- * The PTI (Parallel Trace Interface) driver directs trace data routed from
- * various parts in the system out through the Intel Penwell PTI port and
- * out of the mobile device for analysis with a debugging tool
- * (Lauterbach, Fido). This is part of a solution for the MIPI P1149.7,
- * compact JTAG, standard.
- *
- * This header file is used by n_tracerouter to be able to send the
- * data of it's tty port to the tty port this module sits.  This
- * mechanism can also be used independent of the PTI module.
- *
- */
-
-#ifndef N_TRACESINK_H_
-#define N_TRACESINK_H_
-
-void n_tracesink_datadrain(u8 *buf, int count);
-
-#endif

include/linux/intel-pti.h

···
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- *  Copyright (C) Intel 2011
- *
- * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- *
- * The PTI (Parallel Trace Interface) driver directs trace data routed from
- * various parts in the system out through the Intel Penwell PTI port and
- * out of the mobile device for analysis with a debugging tool
- * (Lauterbach, Fido). This is part of a solution for the MIPI P1149.7,
- * compact JTAG, standard.
- *
- * This header file will allow other parts of the OS to use the
- * interface to write out it's contents for debugging a mobile system.
- */
-
-#ifndef LINUX_INTEL_PTI_H_
-#define LINUX_INTEL_PTI_H_
-
-/* offset for last dword of any PTI message. Part of MIPI P1149.7 */
-#define PTI_LASTDWORD_DTS	0x30
-
-/* basic structure used as a write address to the PTI HW */
-struct pti_masterchannel {
-	u8 master;
-	u8 channel;
-};
-
-/* the following functions are defined in misc/pti.c */
-void pti_writedata(struct pti_masterchannel *mc, u8 *buf, int count);
-struct pti_masterchannel *pti_request_masterchannel(u8 type,
-						    const char *thread_name);
-void pti_release_masterchannel(struct pti_masterchannel *mc);
-
-#endif /* LINUX_INTEL_PTI_H_ */